I woke up this morning and the tank is covered with milt. Does there need to be a female present for the male to do this? If so, I just sexed my other fish. They are way too young to mate, so hopefully they don't go any farther.

did you see the fish chasng each other
or were there any eggs in the tank
if so the other fish is probably female and
if not, its probably not milt because the male
will only use the milt to fertilise the eggs

It happened over night or early morning (I slept in a bit late), so I'm not sure exactly what they were doing. I looked around, but I couldn't find any eggs. I know my ryukin is male because of his breeding stars, but I don't know about my oranda. If it is a female, she's a very young one, so there probably wouldn't have been too many eggs anyway. If there were any, they probably all got eaten. They've been nibbling at the plastic plants quite often the last few days.

Maybe it wasn't even milt. I was told that it was by a friend, because I had never seen it before, and I figured that might be the case because of the spring increase in temp.

Maybe it was just a weird algae or something more sinister (hopefully not). It was kinda a white layer that collected on the walls of the tank and swayed with the current.

it best to do a precautionary water change albert
just in case

and milt just looks cloudy, sort of like a milky colour

Then I guess it wasn't milt after all! I'm guessing it's a weird type of algae then. The new tank gets sunlight on it later in the afternoon and the old tank never got sun on it. I scraped it off the sides after I found it, so the UV will have taken care of it by now.

It is possible that it was milt. However, it disipates rapidly if you have strong aeration or filter action.

Female fish often lay their eggs without a male present. So, I assume male fish could spray milt without a female fish present.

If you see little specks all along the glass then there were eggs stuck there. The fish ate them.